1. Field of the Invention
The present invention relates to a piston-crank mechanism used in a piston engine such as an internal combustion engine or an external combustion engine.
2. Description of the Related Art
In general, friction between the piston and the cylinder comprises at least half of the total friction in a piston engine. Accordingly, there have been various designs in the conventional art that seek to reduce this friction between the piston and the cylinder. For example, in the piston-crank mechanism described in JP2001-50362A, a construction is disclosed wherein the piston and the crank are connected by a free link. This mechanism is constructed so as to ensure that the angle formed by the free link axis relative to the piston central axis at the center of the motion path of the piston is kept as small as possible.
However, because the mechanisms of the conventional art must be increased in size significantly if they are to sufficiently reduce friction, the problem arises that such friction between the piston and the cylinder cannot be reduced sufficiently. Furthermore, an additional problem with the conventional mechanisms is that attaching the mechanism to the piston is a rather complex task.